Impact of Lower Fan shroud on engine temp

I changed my 17 year old radiator a few weeks back (preventative maintenance) along with adding a Trans cooler. In the process, I lost one of the clips to the lower fan shroud and as a result, didn’t install it back. My engine temps dropped from a constant 204, to a 190. My Thermostat jiggle valve was installed at the 12 o clock position when I changed the timing belt and I reinstalled it at the 6 o clock position when I changed the radiator.

I happened to call a local Toyota dealership and they had the lower fan shroud clips available for $0.12/each. For kicks and giggle, I dropped by and purchased 2 and installed the lower fan shroud back into the engine bay.

It’s been 3 days since the lower fan shroud has been installed and I am amazed to tell you that my engine temperature dropped even further.

Old Radiator, Thermostat Jiggle Valve @ 12 o clock: 198 - 206F
New Radiator, Thermostat Jiggle Valve @ 6 o clock, no lower fan shroud: 188 - 192F
New Radiator, Thermostat Jiggle Valve @ 6 o clock, with a lower fan shroud: 185 - 188F

For a small piece of curved plastic, a 3 degree change in temperature is significant. I guess the Engineers knew what they were doing all along. I figured I share this with everyone for your knowledge.

 

But did you use Green or Red coolant?

 

OEM red coolant

 

Good choice

 

Hmm. Did you add the shroud and rotate the thermostat jiggle valve at the same time?

 

you say, engine temp was running 204? That sounds high to me in the first place but I could be wrong. Are you using an ultragauge or scan gauge? My engine maybe hits 194 at its hottest if I’m really driving it. It usually hangs out around
189 Fahrenheit.

I also don’t have my lower fan shroud. So if I did, I would probably be right at the same temp as you.

 

Yes and No. I removed the shroud to replace the radiator. And while everything was out, I rotated the jiggle valve because I was running in the 200F range. I lost the clips to the Lower part of the shroud and only put back the top portion of the shroud when I assembled everything back up. When I installed that small curved piece of shroud back on 3 days ago, the additional 3 degree temperature drop was noticed via ScanGauge.

 

Yep, it was 204. The reason being the Jiggle Valve on the thermostat was at the 12 o clock position. When I rotated it to the 6 o’clock position, the temperature dropped to 190. I’m using ScanGauge to monitor the temperatures.

 

Ahh yes the jiggle valve. Such a small yet impactful detail.
I’ve got an ultragauge, I assume they read the same sensor for engine temp.

I love having a live monitor of the truck. Especially for Check Engine light

 

Jiggle valve on the 3.4 goes at 6 o'clock.

I ran my Tacoma with no shroud for a
Years and it would run upper 180s low 190s most of the time. (2.4L 5 lug manual)